ABSTRACT
OBJECTIVE: The negative predictive value of a normal single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is very high. However, prognostic implication of a normal SPECT MPI in patients with known coronary artery disease (CAD) is not clear. Objective of this study was to evaluate the cardiac event rate in patients with known CAD who had a normal stress SPECT MPI. METHODS: This prospective study accrued 428 consecutive patients with a history of CAD [revascularization or previous myocardial infarction (MI)] who had a normal stress (dynamic exercise or dipyridamole intervention) and rest Tc-99m-MIBI SPECT MPI. These patients were followed for 2-5 years (median: 3.1 years) for all-cause and cardiac mortality and non-fatal MI. Univariate and multivariate analyses were performed to identify predictors of outcome. RESULTS: During a follow-up period, all-cause mortality was found in 60 patients (14%) and 41 (10%) died of cardiac reasons. Non-fatal MI was found in 77 (18%) patients. Annualized cardiac mortality and non-fatal MI rates were 2% and 3.6% respectively. Smoking, congestive heart failure (CHF) and failure to achieve 85% age predicted heart rate were found to be predictors for all-cause and cardiac mortality. Diabetes, dyslipidemia, smoking and limited functional capacity (<7 METS) were found to be predictors for non-fatal MI. CONCLUSIONS: Patients with known CAD had higher cardiac event rates despite a normal stress SPECT MPI. Diabetes, dyslipidemia, smoking and limited functional capacity were the predictors for fatal and non-fatal cardiac events. A cost effective but comprehensive surveillance strategy is warranted.
ABSTRACT
AIMS AND OBJECTIVE: A normal gated myocardial perfusion imaging (GMPI) has been found to have high diagnostic and negative predictive value (NPV) in western population. The goal of the present study was to evaluate the overall and gender-based NPV of a normal GMPI in local population. PATIENTS AND METHODS: This is a prospective study conducted at Nuclear Cardiology Department of Karachi Institute of Heart Diseases (KIHD), Karachi from December 2008 till May 2009. All patients (with intermediate risk) with a normal GMPI with adequate dynamic or dipyridamole stress were included and followed up for 18 months (mean 15 ± 3 months) for fatal or non-fatal infarctions. RESULTS: The mean ejection fraction (EF) of studied population was 69 ± 8% while mean end diastolic (EDV) and end systolic volume (ESV) were 71 ± 19 and 22 ± 11 ml, respectively. In studied female cohort, the mean EF (%), EDV (ml) and ESV (ml) were 71 ± 08, 64 ± 15 and 19 ± 09, respectively. In studied male cohort, the mean EF (%), EDV (ml) and ESV (ml) were 66 ± 06, 82 ± 18 and 27 ± 11, respectively. At 18 months follow-up, one fatal (male patient) and one non-fatal MI (male patient) were reported. The overall NPV was 99.4% over 18 months follow-up with an event rate of 0.6% (95% CI 0.03-1.16%) and annualized event rate of 0.3%. The NPV and annualized event in subgroup analyses, was similar for female and male (P = 0.213). CONCLUSION: We conclude that a normal GMPI with adequate stress in our population has high NPVs for major cardiac events as in western population. In addition, the prognostic utility of GMPI is similar for both men and women.
